4 mm stitch spacing (6.4 SPI)
A 4 mm chisel or pricking iron gives 6.4 stitches per inch (25.4 ÷ 4). It is typical for the most common chisel pitch: bags, straps, sheaths and thicker wallets in 2 to 3 mm leather, with 0.65 mm thread. The calculator below is set to 4 mm: enter your seam length to see how many holes fit and whether the last one lands on the corner.
Doing this on a whole pattern? EasyPatt places the holes for you on every edge, shows the count per side, and prints the pattern to scale — free, in your browser.
Hole chart for 4 mm
How many holes fit on common seam lengths at 4 mm, both ways of handling the corner. Land on both corners rounds to a whole number of stitches and shows the resulting spacing; exact spacing keeps 4 mm and shows what is left at the end.
| Seam | Holes, both corners | Spacing used | Holes, exact | Left over |
|---|---|---|---|---|
| 50 mm | 14 | 3.85 mm (−0.15 mm) | 13 | 2.00 mm |
| 60 mm | 16 | 4.00 mm (exact) | 16 | 0.00 mm |
| 80 mm | 21 | 4.00 mm (exact) | 21 | 0.00 mm |
| 100 mm | 26 | 4.00 mm (exact) | 26 | 0.00 mm |
| 120 mm | 31 | 4.00 mm (exact) | 31 | 0.00 mm |
| 150 mm | 39 | 3.95 mm (−0.05 mm) | 38 | 2.00 mm |
| 200 mm | 51 | 4.00 mm (exact) | 51 | 0.00 mm |
| 250 mm | 64 | 3.97 mm (−0.03 mm) | 63 | 2.00 mm |
| 300 mm | 76 | 4.00 mm (exact) | 76 | 0.00 mm |
Any other length: type it into the calculator above. All numbers come from the same code that places stitch holes in the EasyPatt editor.
Other spacings
2.7 mm 3 mm 3.38 mm 3.85 mm 5 mm 6 mm 6 SPI 7 SPI 8 SPI Any spacing
How the calculator works
The number of gaps between holes is the seam length divided by the spacing. A 120 mm seam at 4 mm gives 30 gaps and 31 holes, and the last hole lands exactly on the corner. Most seams are not that tidy. At 125 mm you get 31.25 gaps, and you have to choose.
Land on both corners (balancing)
Round the gaps to a whole number, 31, and divide the length by it: 4.03 mm per stitch. The difference from 4 mm is invisible, and the seam starts and ends on a hole. This is the default here and in EasyPatt, and it is the right choice for anything with visible corners: wallets, card holders, bag flaps.
Keep exact spacing (walking)
Keep 4 mm exactly, get 31 gaps, and leave the 1 mm remainder at the end. This matches what a pricking iron does when you walk it along an edge from one corner. Fine for a long edge whose end is hidden or trimmed later, or when the remainder is under a third of the spacing.
With irons, the practical trick for balancing is to mark from both corners toward the middle, so the adjustment ends up mid-seam where nobody looks. Read more in the saddle stitch spacing guide.
SPI to mm conversion
Stitches per inch is the American convention; millimetres the European one. The conversion is 25.4 ÷ SPI.
| SPI | Spacing | Typical use |
|---|---|---|
| 4 | 6.35 mm | Heavy belts, holsters |
| 5 | 5.08 mm | Belts, heavy bags |
| 6 | 4.23 mm | Bags, sheaths |
| 7 | 3.63 mm | Wallets, straps |
| 8 | 3.18 mm | Fine wallets, watch straps |
| 9 | 2.82 mm | Thin lining leather |
| 10 | 2.54 mm | Very fine work |
Chisels sold in millimetres rarely match a whole SPI: a 3.38 mm chisel is 7.5 SPI, a 3.85 mm chisel is 6.6 SPI. Type the number on the chisel into the calculator and it shows the SPI.
Common questions
How many stitches per inch is 4 mm?
A 4 mm spacing is 6.35 stitches per inch: 25.4 mm in an inch divided by 4.
What is 4 mm stitch spacing used for?
Typically the most common chisel pitch: bags, straps, sheaths and thicker wallets in 2 to 3 mm leather, with 0.65 mm thread.
How many holes fit on a 100 mm seam at 4 mm?
26 holes with one on each corner, using 4 mm between them.
The calculator uses the same code that places stitch holes in the EasyPatt editor, so the numbers here match what you will see on a printed pattern.